1. Field of the Invention
This invention relates to an air-cooled internal combustion engine.
2. Description of the Related Art
Conventional internal combustion engines of the type to which the present invention is directed include the following problems:
(1) A cam shaft and a balancing shaft are arranged separately on the left and right sides of a crank-shaft, and a heavy starting motor is positioned above the crank-shaft at the balancing shaft side of the crankshaft. Consequently, the engine has a high center of gravity, a large overall engine height, and an objectionable vibration noise sound level.
(2) As for a cooling structure, in Japanese unexamined Utility Model Publication No. 63-20821 for example, an air cleaner is disposed on the same side as a fan cover and cooling air sent from a cooling fan into a cylinder head is exhausted and dispersed in different directions, so that it is difficult to collect exhausted air into one spot. Therefore, it becomes difficult and requires a complicated arrangement to provide an exhaust air disposal mechanism when mounting such an engine on an operation machine.
(3) In the Japanese unexamined Utility Model Publication No. 63-20821, an exhaust muffler is connected to an exhaust port through a simple exhaust pipe and counter-measures against noise are not taken.
(4) The fuel injection valve is also not covered by a cylinder head cover so that a problem results due to noise emitted from around the fuel injection nozzle.
(5) The fuel tank is also supported directly on the engine body. Therefore, vibration-proof members should be attached to all supporting parts and this makes the supporting mechanism complicated.
(6) Also, with respect to the position of the air cleaner or the position of the air cleaner relative to the fuel injection pump, the air cleaner is not utilized as a means for reducing noise.